In some motor drive apparatuses for a conventional electric power steering system (EPS), which assists a steering operation of a driver by driving force of a motor, a motor and an electronic control unit for controlling the motor are integrated. For example, in a motor drive apparatus according to JP 2011-177001A (US 2011/0018374 A1), a semiconductor module is provided on a heat sink to promote heat radiation.
In this motor drive apparatus, however, the heat sink is encapsulated within a cover and hence the heat radiation performance of the heat sink is not sufficient.